Concept:Foreign policy decisions can be triggered by actions that threaten national or regional security.Explanation:France conducted an atomic bomb test in the Sahara Desert in 1960.This test took place close to Nigeria’s border and raised serious environmental and security concerns.In response, the Nigerian government, led by Prime Minister Balewa, severed diplomatic ties with France in 1961.The action was a protest against France’s nuclear testing in Africa.Answer:A. France's atomic test in the Sahara Desert.